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514094f9 1<?xml version='1.0'?>
65eb4378 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
12b42c76 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
65eb4378 4
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5<!--
6 SPDX-License-Identifier: LGPL-2.1+
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7-->
8
3715a071 9<refentry id="hwdb" conditional="ENABLE_HWDB">
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10 <refentryinfo>
11 <title>hwdb</title>
12 <productname>systemd</productname>
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13 </refentryinfo>
14
15 <refmeta>
16 <refentrytitle>hwdb</refentrytitle>
17 <manvolnum>7</manvolnum>
18 </refmeta>
19
20 <refnamediv>
21 <refname>hwdb</refname>
22 <refpurpose>Hardware Database</refpurpose>
23 </refnamediv>
24
25 <refsect1><title>Description</title>
26 <para>The hardware database is a key-value store for associating modalias-like keys to
a8eaaee7 27 udev-property-like values. It is used primarily by udev to add the relevant properties
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28 to matching devices, but it can also be queried directly.</para>
29 </refsect1>
30
31 <refsect1><title>Hardware Database Files</title>
32 <para>The hwdb files are read from the files located in the
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33 system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
34 the local administration directory <filename>/etc/udev/hwdb.d</filename>.
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35 All hwdb files are collectively sorted and processed in lexical order,
36 regardless of the directories in which they live. However, files with
37 identical filenames replace each other. Files in <filename>/etc</filename>
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38 have the highest priority and take precedence over files with the same
39 name in <filename>/usr/lib</filename>. This can be used to override a
40 system-supplied hwdb file with a local file if needed;
65eb4378 41 a symlink in <filename>/etc</filename> with the same name as a hwdb file in
12b42c76 42 <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
dc17ee3d 43 disables that hwdb file entirely. hwdb files must have the extension
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44 <filename>.hwdb</filename>; other extensions are ignored.</para>
45
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46 <para>Each hwdb file contains data records consisting of matches and associated
47 key-value pairs. Every record in the hwdb starts with one or more match strings,
48 specifying a shell glob to compare the lookup string against. Multiple match lines
49 are specified in consecutive lines. Every match line is compared individually, and
50 they are combined by OR. Every match line must start at the first character of the
51 line.</para>
65eb4378 52
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53 <para>The match lines are followed by one or more key-value pair lines, which are
54 recognized by a leading space character. The key name and value are separated by
55 <literal>=</literal>. An empty line signifies the end of a record. Lines beginning
56 with <literal>#</literal> are ignored.</para>
57
58 <para>In case multiple records match a given lookup string, the key-value pairs
59 from all records are combined. If a key is specified multiple times, the value
60 from the record with the highest priority is used (each key can have only a single
61 value). The priority is higher when the record is in a file that sorts later
62 lexicographically, and in case of records in the same file, later records have
63 higher priority.</para>
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64
65 <para>The content of all hwdb files is read by
66 <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
67 and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
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68 or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the
69 compiled database in an immutable image. During runtime, only the binary database
70 is used.</para>
71 </refsect1>
72
73 <refsect1>
74 <title>Examples</title>
75
76 <example>
77 <title>General syntax of hwdb files</title>
78
79 <programlisting># /usr/lib/udev/hwdb.d/example.hwdb
80# Comments can be placed before any records. This is a good spot
81# to describe what that file is used for, what kind of properties
82# it defines, and the ordering convention.
83
84# A record with three matches and one property
85mouse:*:name:*Trackball*:
86mouse:*:name:*trackball*:
87mouse:*:name:*TrackBall*:
88 ID_INPUT_TRACKBALL=1
89
90# A record with a single match and five properties
91mouse:usb:v046dp4041:name:Logitech MX Master:
92 MOUSE_DPI=1000@166
93 MOUSE_WHEEL_CLICK_ANGLE=15
94 MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
95 MOUSE_WHEEL_CLICK_COUNT=24
96 MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
97</programlisting>
98 </example>
99
100 <example>
101 <title>Overriding of properties</title>
102
103 <programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
104evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
105 KEYBOARD_KEY_a1=help
106 KEYBOARD_KEY_a2=setup
107 KEYBOARD_KEY_a3=battery
108
109evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn123*
110 KEYBOARD_KEY_a2=wlan
111
112# /etc/udev/hwdb.d/70-keyboard.hwdb
113# disable wlan key on all at keyboards
114evdev:atkbd:*
115 KEYBOARD_KEY_a2=reserved</programlisting>
116
117 <para>If the hwdb consists of those two files, a keyboard with the lookup string
118 <literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pn123</literal>
119 will match all three records, and end up with the following properties:</para>
120
121 <programlisting>KEYBOARD_KEY_a1=help
122KEYBOARD_KEY_a2=reserved
123KEYBOARD_KEY_a3=battery</programlisting>
124 </example>
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125 </refsect1>
126
127 <refsect1>
128 <title>See Also</title>
129 <para>
130 <citerefentry>
131 <refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
132 </citerefentry>
133 </para>
134 </refsect1>
135</refentry>